Year	Number
1971	63976
1972	217570
1973	342503
1974	482481
1975	634284
1976	707318
1977	689877
1978	689202
1979	889209
1980	1198676
1981	1697008
1982	1549904
1983	1742981
1984	2887861
1985	3695400
1986	4604200
1987	5209300
1988	5581300
1989	6006500
1990	6258000
1991	6526000
1992	6855000
1993	7392000
1994	8157000
1995	9124841
1996	10090627
1997	10878677
1999	12752383
2000	12327079
2003	11298031
2006	15306302
2007	17228669
2008	18906427
2009	19777488
2010	20419354
2011	20299603
2012	19696392
2013	21140347
2014	19233849
2015	17555320
2016	16569753
2017	15992821
2018	15927388